Amazing how much you can learn from this forum! Thanks all!
I hope one day I’ll be able to contribute something myself.

Till then, I wonder if you could help me with this: while I
find 1005Phillip’s method of “squeezing” more data from the broker absolutely
ingenious (https://www.mql5.com/en/forum/124619)
, I wonder how you can PRESERVE chart data – once you have it. If I close a
chart, after a while, the data seems to “go away”. Does it mean I always have to keep open all the charts I’m
interested in? Or would it be enough to include the corresponding pairs in
MarketWatch?

Any advice on how I can keep whatever data I already have for a pair ?...

If I have considerably more than 260,000 on a chart, it drastically slows everything down.

Anyways, I get it that there is no other way to collect new bars than leaving the charts open, but do they have to be open all the time? Too many open charts will slow everything down as well, won't they?

And can I guess from your question about max bars in history that, once a chart is full with bars, the oldest bars don't "go away" but move to the history "department"?

Any thread or info source that I can go to for the dynamics between chart bars, history bars, old and new bars, refreshes, etc...?